Insertion of a hemiarthroplasty is a well established treatment for a dislocated medial hip fracture in elderly patients. The purpose of this study is to compare unipolar and bipolar hemiarthroplasty as a treatment for patients aged 70 years or above with a dislocated medial femoral neck fracture. The study is prospective and randomised, and will be based on questionnaires, clinical examinations, registration of complications and radiographic evaluation at follow up at 3 months, 1 and 3 years postoperatively.